From: Matt C <canimal@...>
Date: 2005-06-30T10:05:43+09:00
Subject: Q: inheriting from Array, overloading []

New to Ruby.  Probably my terminology will be a bit off.

In the Pickaxe book (first edition) they show a clever little trick with 
the SongList class, where you can use [] to pull a song from the list using 
either the integer index or the name of the song.

I wanted to try something like that, but with a subclass of Array rather 
than writing a wrapper around an array.  I had the idea I might be able to 
use super:

class TalkerArray < Array    #will hold a collection of Talkers.

  def [](key)
    if key.kind_of?(Integer)
      return super[key]
    else
      return self.find{|t| t.name = key}  #talkers have .name property.
    end
  end

end

but it didn't work (*).  I bet there is a simple way to make something like 
this work while inheriting from Array, though.  Can anyone show me?

Thanks,
Matt



*:  The error message I got was strange:

E:/matt/ruby/usr/ww/chat.rb:173:in `[]': undefined method `[]' for #
<Talker:0x2a5be68 @name="bob", @last_msg=0> (NoMethodError)

Why the heck is it looking at the Talker object?  I must not understand 
what 'super' does.  Anyway, I put this as a postscript because it's kind of 
a side issue for me.  I'm guessing I don't really need 'super', or 
understanding 'super', to override [] the way I want to.  So I can worry 
about that some other day.  Which is not to say I won't listen if someone 
wants to explain,  it's just not my priority of the moment.  Ok, really 
done typing now.